1. Field of the Invention
This invention relates to polymerizable unsaturated polyester resin syrup compositions, to methods of curing such polymerizable unsaturated polyester resin syrup compositions in an alkaline admixture with significant quantities of aqueous alkali metal silicate, preferably sodium silicate, and to the thermoset products obtained thereby.
2. Description of the Prior Art
Unsaturated polyester resin syrups are employed in the production of coatings, molded, cast and hand-lay-up products such as flat and profiled building sheets, automobile fenders and other shaped components, furniture, plumbing fixtures, duct work, boats, electrical component housings, electrical circuit boards, and the like. The unsaturated polyester resin syrups are frequently reinforced with fibrous fillers, customarily glass fibers and may be extended with inert particulate fillers such as wood flour, silica, glass beads, clay, calcium carbonate and the like. See Polyesters and Their Applications, Bjorksten et al, Reinhold Publishing Corporation, New York 1960 (4th printing).
Unsaturated polyester resin syrups also have been extended by dispersing water in the resin in the form of small droplets to create a water-in-resin emulsion. Such emulsions have been described as containing 40 to 85 percent by weight water in combination with 15 to 60 percent by weight of unsaturated polyester syrups. See U.S. Pat. No. 3,591,191. Compositions containing 50 to 80 percent by weight of water in a mixture of water and unsaturated polyester resin syrup are described in U.S. Pat. No. 3,687,883. The addition of small quantities of sodium silicate to the water phase of the water-in-resin emulsions has been described. See German Offenlegungsschrift No. 1,962,393.
Unsaturated polyester resin syrups have been combined with solid sodium silicate and with liquid sodium silicate and thereafter reacted with dolomite, U.S. Pat. No. 3,392,127 and its counterparts British Pat. Nos. 925,625 and 960,961 and France patents Nos. 1,195,743 and addition patent No. 81,527. This source of technology asserts that liquid sodium silicate cannot be mixed with more than 0.3 times its weight of unsaturated polyester resin syrup prior to addition of dolomite.
Unsaturated polyester resin syrup has been combined with aqueous sodium silicate in a non-alkaline mixture to produce microporous articles. See U.S. Pat. No. 2,505,353.
Small quantities of silica aerogel have been employed as thickeners for unsaturated polyester resins, U.S. Pat. No. 2,610.959.